That was a really close call with the Weevil. It's nice that Ianto was there to help and probably good that she won't remember what happened. Next time she should wear better shoes. Those sewer grates can be pretty hazardous.
Author's Response: She was nowhere near the sewer grate when she fell though. Ianto is the king of cover-up - while the rest of the team dealt with the Weevil, he was retconning Kathy and staging the 'accident'. She will never know. Thank you!